r N D E X.

Objects, why they appear erect, notwith-standing their images are inverted inthe eye 132

- why they appear coloured whenscen through forne telescopes 143Opera-glass 148

Optic nerve, why that part of the imagewhich falls upon it is lost 133, 134

P.

Padmore (Mr.) his improvement of cranes

Per oeci 166

Perfian wheel 93

Pile-engine 61

Planetary motions (the laws thereof) 15Poles of the earth and heavens 154, 156Polar circles 159

Porosity of bodies xo

Precepts for calculating the mean times- of new and füll moons and eclipses. 238Prifmatic colours 150

—————— make a white whea

blended together 151

Pulley 36

Pump, common 73

- - forcing 76

—— engine to work by water 78

. by horfes ibid.

•Pyrometer 10

Qi

Quantity of matter in bodies,

is in exact

proportion to their weight

6

Quickfilver, ita WClgtlt

106

R.

Rain-bow

152

Rays of light

124

Repulsion

5

Right ascension

186

Running water, its weight

86

8 .

Sails of a wind-mill, their proper form and

angle

5 i

> ■■■■■ —their incredible velo-

city

5 *» 52

Screw, its power

43

■ fhewn by a machine

ibid.

Seafons, how they may be fhewn by a-fmall globe 159

Signs of the zodiac J 158

Silver, how much heavier than its bulkof water 95

Slare (Dr.) his dangerous experiment

124

Solidity of matter 1

Specific gravities of bodies 93

Spectacles, why forne eyes require them

o • . rZ4

Spirituous liquors, to know whether theybe genuine or not 98

Spouting fiuids 69

Steam (or sire) engine 87

Steelyard 32

Sun, appears above the horizon when heis really below it 126

Syphon 70

T.

Tantalus’s cup 71

Table of the quantity of water thatmay be raifed to any given height by acommon pump 76

■ ' of sines for the elevation of wa-

ter-pipes 82

——— of the quantity and weight of wa-ter in a pipe of a given lengtb, anddiameter of bore 84—89

—-of the power of the steam en-gine 92

— — ... 0 f specific gravities 96, 97

———-of troy weight reduced to avoir-dupoise 101

■“ of avoirdupuifw jcduced to

troy 102

--of the rarity and expansion of air

105

—^—— of the miles in a degree of lon-gitude in all latitudes x68

--of the fun’s place and declina-

tion _ 212—217

Tables for calculating new and füll moons

and eclipsesTelescopes, refracti ng

Temperate zonesThermometerThunder and lightningToricellian experimentTorrid zone

and

249—252reflecting137—146170

99

109

105

170

Trade-